Possible role of the hormonal form of vitamin D3 in the granuloma-associated angiotensin-converting enzyme activity.

We studied effects of the hormonal form of vitamin D3 on the angiotensin-converting enzyme (ACE) activity of hepatic granulomas in mice infected with Schistosoma mansoni. During 7 to 11 weeks after infection, mice were given orally 0.1 or 1.0 microgram/kg of 1 alpha (OH)D3 or only medium solution every other day. Granulomatous livers were removed at 7, 9 and 11 weeks after infection, and ACE activity was measured in the granulomas isolated from each liver tissue using a fluorometric method. Oral administration of 0.1 or 1.0 microgram/kg/2 days of 1 alpha (OH)D3 for 4 weeks significantly enhanced ACE activity in the granuloma tissue. Since the DNA content relative to a unit weight of protein in the granulomas did not change with the 1 alpha (OH)D3 treatment, it is suggested that the elevated tissue ACE activity is due to an actual increase of the enzyme activity in each granuloma cell. The present observation may have relevance to sarcoid granulomas characterized by an increased tissue ACE activity, since macrophages from patients with sarcoidosis synthesize a biologically active hormonal form of vitamin D3. Namely hormonal form of vitamin D3 locally produced by macrophages is involved not only in systemic Ca++ metabolism but also in the stimulation of macrophages themselves to produce ACE in the granulomas.